This invention relates to safety gear transmissions for snow clearing vehicles, particularly blower type snow ploughs and rotary snow ploughs.
It is desirable that all vehicles equipped with snow clearing units should incorporate safety gear change transmissions, because of the fact that during use of such vehicles there is always a danger than the snow clearing unit will hit an obstacle that is covered by snow and therefore will not be visible to the driver of the vehicle. When blower type snow ploughs are used having a rotary blower unit fitted to the front of the vehicle, the expensive blades are frequently damaged by encountering solid obstacles. Up to the present time the extent of such damage has largely been limited by controlling the speed of the vehicle and the speed of the driver's reaction on striking such an obstacle. In conventional existing vehicles the drivers only recourse, upon first hearing or feeling that a collision with an obstacle had occurred, was to depress the clutch pedal of the vehicle placing the transmission in neutral, and thereafter applying the brakes, so that the continued advance of the vehicle ceased as quickly as possible. However, the interruption of the vehicle drive occurring on depression of the clutch pedal unfortunately does not cause the vehicle to stop instantaneously, even when moving quite slowly. Under snow conditions, the use of brakes is not of much help. Due to the inertia of the vehicle it still continues to move on with the result that uncontrollable damage can occur in the short time before the vehicle eventually stops.
The object of the present invention is to substantially reduce or avoid the damage which can occur to a vehicle of the type described on hitting an obstacle.
It is a particular object of the present invention to provide an automatic gear changing mechanism for a snow-clearing vehicle that automatically shifts the vehicle into reverse gear upon reaction to the sighting or to the striking of an obstacle in its path of travel.
These objects as well as others together with several advantages will be apparent from the following disclosure.